I need to wire a total of four LED driving lights (12 volt, 40 watts per light) that I need to control as two pairs (2 left lights / 2 right lights), with each pair switched by two different means, using the same power source (the vehicles' 12 volt system).

To explain a bit more, the lights will be used in two different modes:

  • In mode one (normal) they are operated in pairs using a typical switched relay circuit with power supplied via an auxiliary fuse box connected to the vehicles battery;
  • In the second mode (emergency) the lights again will use a typical switched relay circuit via the fuse box, but this circuit includes the addition of a "wig-wag" LED alternating flasher relay (2-channel 240 watt / 120 watt each channel) which would then connect to a common lighting harness used by both the "normal mode" circuit and this second "emergency mode" circuit.

Sorry if this is completely confusing, but being new to this sort of thing I'm unsure how best to describe my problem and more unsure that this will even work without damaging some or all of the components.

I've been told to "use diodes" without being told the necessary particulars, such as what kind of diode and where.

Thanks in advance to anyone that can help!

  • 1
    \$\begingroup\$ I'd make a diagram of what your are trying to accomplish and show the circuit as it stands. It's hard to help without at least some sort of diagram. \$\endgroup\$
    – David
    Aug 31, 2020 at 20:45

1 Answer 1


Here's a way, using electromagnetic relays.

enter image description here

Three relays have been shown.

Actually a single 3PDT relay would suffice.

Diodes have been avoided, considering the voltage drop they would cause.


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